This invention is concerned with a machine for roughing side wall portions of a shoe comprising a shoe support, for supporting a shoe with side wall portions thereof to be roughed exposed, a rotary roughing tool supported by a tool support and comprising a plurality of roughing elements mounted for movement in a direction towards and away from the centre of rotation of the tool, the arrangement being such that said elements are urged centrifugally away from said centre by the rotation of the tool, and means for effecting relative movement, in directions extending lengthwise, widthwise and heightwise of the bottom of a shoe supported by the shoe support, between the shoe support and the tool support, whereby the tool is caused to operate progressively along the exposed side wall portions of a shoe supported by the shoe support.
One such machine, is described in co-pending U.S. patent application Ser. No. 377,237 and comprises a shoe support for supporting, bottom uppermost, a shoe with side wall portions thereof to be roughed exposed, said shoe support being mounted for movement along an arcuate path in a direction extending lengthwise of the bottom of a shoe supported thereby, together with a tool support for supporting a rotary roughing tool for movement both widthwise of the bottom of a shoe supported by the shoe support and also heightwise thereof. The means for effecting such relative movement between the shoe support and the tool support comprises a plurality of n.c. motors, e.g. stepping motors, which operate under computer control, in accordance with a programmed instruction in the form of digitised coordinate axis values, to cause the tool to operate progressively along the exposed side wall portions of a shoe supported by the shoe support.
It will be appreciated that, by using a tool of the type referred to above, any variations between the digitised path and the actual shoe shape can be accommodated by greater or less outward movement of the roughing elements, without significantly affecting the quality of the rough.
For determining the path of the tool relative to shoe side wall portions in said machine reference is made to U.S. Pat. No. 4,541,054, in which is set out a method of digitising the bottom of a shoe by determining the coordinates of a plurality of points spaced equi-distantly from one another along the marginal portions of the shoe bottom and storing such points in the form of digitised coordinate axis values. From these points the path of a tool along the marginal portions of a shoe bottom can then be determined. Such a method is also applicable in the case of operating along side wall portions of shoes, except that whereas, in operating on marginal portions of shoe bottoms using a rotary radial roughing tool, the point of contact between the tool and the shoe bottom represents the point which is being actually digitised, in the case of side wall roughing using a rotary radial roughing tool the point of contact of the tool with the side wall is offset from the actual point of digitising by a distance equal to the radius of the tool.
Under such circumstances, it will be appreciated, if the digitised points are spaced equi-distantly, in the region of relatively sharp curvature, e.g. the toe end and heel end of shoes, the points of contact between the tool and side wall of the shoe corresponding to the digitised points will be spaced more closely together. Bearing in mind that, by spacing the points equi-distantly in accordance with the method of U.S. Pat. No. 4,541,054, the speed of relative movement between the tool and the side wall portions of the shoe (the traverse speed of the tool) remains constant or substantially so, it will be appreciated that the reduction of the notional distances between points of . contact as described above will have the effect of reducing the traverse speed of the tool in the region of such areas of sharp curvature, namely the toe end and heel end of the shoe. Such a reduction in the traverse speed of course means that the tool operates for a relatively longer period in such areas.
Because of the type of tool used, such reduction in the traverse speed of the tool means that the degree of roughing in such areas is greater than that along the relatively straight side wall portions, which may be detrimental in the finished shoe.
It would of course be possible to digitise the shoe bottom in a different manner so that the path of the operating surface of the tool contacting the shoe is determined and stored in the form of digitised coordinate axis values, in the same way as currently effected in the case of the roughing of marginal portions of shoe bottoms. In such a case, however, it would then be necessary to project the centre of the tool, in order to determine the corresponding path of relative movement between the shoe support and the tool support. Such an arrangement, however, would require a greater amount of computing power, especially bearing in mind that the angle of projection outwardly from the digitised point of contact has to be calculated for each point, which will of course vary according to the location of the particular point along the periphery of the shoe bottom. In addition, it has to be borne in mind that such an arrangement would vary the speed of relative movement between the tool support and the shoe support. In order to obtain an optimum output for the machine, however, desirably the speed of relative movement between the tool support and the shoe support is kept at a maximum during the operation of the machine, so that if the speed is maintained at a maximum as the tool operates around the toe and heel ends of the shoe, necessarily the speed along the side portions of the shoe will be less than the maximum, which is of course detrimental to the machine output.